Note: Descriptions are shown in the official language in which they were submitted.
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HYDROGEN STORAGE AND SUPPLY METHOD
Field of the Invention
[0001] The present invention relates to a system and
method for supplying hydrogen to a polymer membrane
fuel cell to power a load and that is operated on a
scheduled basis to maintain the polymer membrane in a
hydrated condition. More particularly, the present
invention relates to such a system and method in which
the hydrogen used for maintenance purposes is stored in
and supplied from an auxiliary gas cylinder.
Background of the Invention
(0002] Fuel cells provide an environmental friendly
method for generating electricity for a variety of
purposes. One major purpose is to provide a back-up
supply of electricity in case of power outages. As can
be appreciated, if hydrogen is used as a fuel, there
are less pollutants produced than in the case of back-
up electrical generation that involve the use of
internal combustion engines.
[0003] Where fuel cells are used to supply back-up
power and for other uses, a sufficient amount of
hydrogen must be stored to allow the fuel cell to
supply a specific amount of electrical energy for the
particular load involved. For instance, the
specification might be to supply 5 kilowatts of power
for 8 hours. Storage of hydrogen for fuel cells that
utilize polymer membranes is complicated by the fact
that such a fuel cell must be powered up in accordance
with a schedule, for instance, every month for 15
minutes, in order to ensure that the membrane remains
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properly hydrated. The problem with this is that the
scheduled maintenance operation of the fuel cell will
consume hydrogen that otherwise must be on hand to
ensure that the fuel cell will be able to meet its
intended power requirements.
[0004] As may be appreciated, the continuing
requirement to recharge a bulk hydrogen supply is a
logistically complex if not expensive proposition. For
instance, in order to recharge a bulk hydrogen supply,
a tube trailer or other heavy equipment is required.
Further expense may be produced where the fuel cell is
situated in a geographically remote location. The
present invention overcomes this problem by providing a
hydrogen supply system and method for a fuel cell
employing a polymer membrane that does not require the
use of heavy equipment and the like to insure that
there is sufficient hydrogen banked for later use by
the fuel cell.
Summary of the Invention
[0005] The present invention provides a hydrogen
storage system for supplying hydrogen to a fuel cell
employing a polymer membrane to power a load in
accordance with a predetermined electrical power
requirement and to maintain the polymer membrane in a
hydrated condition.
[0006] In accordance with the present invention, a
main hydrogen storage site is provided. The main
hydrogen storage site is sized to contain at least a
sufficient amount of hydrogen for the fuel cell to
generate the predetermined electrical power
requirement. An auxiliary hydrogen storage site is
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sized to contain an amount of hydrogen that is at least
sufficient to allow the fuel cell to operate on a
scheduled basis to maintain the polymer membrane in
hydrated condition. A manifold connects the main
hydrogen storage site and the auxiliary hydrogen
storage site and has an outlet to deliver the hydrogen
to the fuel cell. The manifold is configured to allow
the auxiliary hydrogen storage site to be renewed
independently of the main hydrogen storage site. The
manifold has a flow control network to allow the fuel
cell to draw the hydrogen from the auxiliary hydrogen
storage site to maintain the polymer membrane in the
hydrated condition, without utilization of the hydrogen
from the main storage site.
[0007] The flow control network can have pressure
regulators configured such that the hydrogen from the
auxiliary hydrogen storage site is delivered to the
outlet before the hydrogen stored in the main hydrogen
storage site. Check valves are provided to prevent the
flow of hydrogen between the main and auxiliary
hydrogen storage site. Thus, for membrane maintenance
purposes, hydrogen is drawn from the auxiliary hydrogen
storage site. When the fuel cell is required to power
the load, for instance, as power back-up, any remaining
hydrogen is drawn from the auxiliary hydrogen storage
site and then from the main hydrogen storage site.
Since the amount of hydrogen stored in the auxiliary
site is sufficient for the maintenance operation, there
will always be a sufficient amount of hydrogen in the
main storage site to allow the fuel cell to meet its
power requirements.
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[0008] The main hydrogen storage site can consist of
two banks of compressed gas cylinders and the auxiliary
hydrogen storage site can be a single compressed gas
cylinder. In such case, the pressure regulators can be
first, second and third pressure regulators associated
with a single compressed cylinder and one and the other
of the two banks of the compressed gas cylinders,
respectively. An outlet pressure regulator is provided
to adjust the outlet pressure of the hydrogen at the
outlet of the manifold. The first pressure regulator
is set at a higher pressure than the second pressure
regulator which is in turn set at a higher pressure
than the third pressure regulator. As a result, the
hydrogen is first drawn from the single compressed gas
cylinder and then the one of the two banks of the
compressed gas cylinders. After the pressure has
sufficiently dropped in the one bank of compressed gas
cylinders, then the other of the two banks of
compressed gas cylinders is used to deliver the
hydrogen. This all occurs automatically without the
use of any electronic controls or expensive remotely
operated valves.
[0009] The two banks of cylinders can be connected
to the manifold to commonly feed the manifold with
hydrogen. In such case, the pressure regulators are
first and second pressure regulators associated with
the single compressed gas cylinder and the two banks of
compressed gas cylinders, respectively. The first
pressure regulator is set to a higher pressure than the
second pressure regulator such that the hydrogen is
first drawn from the single compressed gas cylinder to
the outlet.
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[0010] In another embodiment, the main h-ydrogen
storage site can be a composite, carbon-fiber wrapped
compressed gas cylinder. The auxiliary storage site is
a single compressed gas cylinder. The pressure
regulators are a first pressure regulator associated
with a single compressed gas cylinder and second and
third pressure regulators associated with the
composite, fiber-wrapped compressed gas cylinder. An
outlet pressure regulator is provided to the outlet
pressure of the hydrogen at the outlet of the manifold.
The second and third pressure regulators are situated
in an in-line relationship to regulate pressure of the
hydrogen supplied from the composite, carbon-fiber
wrapped compressed gas cylinder to level below that
regulated by the first pressure regulator. As a
result, hydrogen is first drawn from the single
compressed gas cylinder to the outlet. As can be
appreciated, two pressure regulators are required in
case of a composite, carbon-fiber wrapped compressed
gas cylinder which can be designed to obtain the
hydrogen at over 5,000 lbs.
[0011] In another aspect, the present invention
provides a method for supplying a hydrogen to a fuel
cell employing a polymer membrane to power a load in
accordance with a predetermined electrical power
requirement and to maintain the polymer membrane in a
hydrated condition. Hydrogen is supplied to the fuel
cell to generate electricity to power the load from a
main hydrogen storage site charged with at least a
sufficient amount of hydrogen for the fuel cell to
generate the predetermined electrical power
requirement. Hydrogen is also supplied to the fuel
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cell on a scheduled basis from an auxiliary hydrogen
storage site charged with an amount of hydrogen that is
at least sufficient to maintain the polymer membrane
hydrated. The auxiliary hydrogen storage site is
periodically renewed so that it remains charged with
the amount of hydrogen to allow the fuel cell to
operate on the scheduled basis without drawing hydrogen
from the main hydrogen storage site.
[0012] The hydrogen can be delivered from both the
main hydrogen storage site and the auxiliary hydrogen
storage site to a manifold having an outlet to the fuel
cell. The manifold can have check valves to present
the flow of hydrogen from the auxiliary hydrogen
storage site to the main hydrogen storage site and
vice-versa. The hydrogen from the auxiliary hydrogen
storage site is delivered to the manifold at a higher
pressure than that of the main hydrogen storage site so
that the hydrogen will be first drawn from the
auxiliary hydrogen storage site.
[0013] The auxiliary hydrogen storage site can be a
single compressed gas cylinder and the auxiliary
hydrogen storage site can be renewed by periodically
replacing the single compressed gas cylinder. Where a
manifold is employed, the auxiliary hydrogen storage
site can be renewed by periodically disconnecting the
single compressed gas cylinder from the manifold and
replacing the single compressed gas cylinder.
Brief Description of the Drawings
[0014] While the specification concludes with claims
distinctly pointing out the subject matter that
applicants regard as their invention it is believed
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that the invention will be better understood when taken
in connection with the accompanying drawings in which:
[0015] Fig. 1 is a schematic illustration of a
hydrogen supply system for carrying out a method in
accordance with the present invention;
[0016] Fig. 2 is an alternative embodiment to Fig.
1; and
[0017] Fig. 3 is an alternative embodiment of Fig.
1.
Detailed Description
[0018] With reference to Fig. l, if a hydrogen
storage system 1 is illustrated for supplying hydrogen-
to a polymer membrane fuel cell (not illustrated). The
polymer membrane fuel cell is employed to generate
electricity to power a load in accordance with the
predetermined electrical power requirement, for
instance, as back-up power. The polymer membrane fuel
cell also operates on a scheduled predetermined basis
to maintain the polymer membrane in a hydrated
condition. The fuel cell itself is activated for the
foregoing purposes by known automated means that
activate the fuel cell upon the occurrence of, for
instance, a power upset or on the scheduled basis to
maintain the polymer membrane.
[0019] Hydrogen storage system 1 is provided with
first and second banks 10 and 12 of compressed gas
cylinders 14 that are connected to one another. The
resultant main hydrogen storage site is sized to
contain at least a sufficient amount of hydrogen for
the fuel cell to generate the predetermined electrical
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_ g
power requirement. As may be appreciated, more
hydrogen can be stored to provide a factor of safety.
An auxiliary hydrogen storage site is formed by a
single compressed gas cylinder 16 that is sized to
contain an amount of hydrogen that is at least
sufficient to allow the fuel cell to operate on the
scheduled basis. Again, more hydrogen could be stored
in compressed gas cylinder 16 to provide a factor of
safety.
[0020] First and second banks of hydrogen cylinders
and 12 and auxiliary compressed gas cylinder 16 are
connected to a manifold 18 having an outlet 20 to the
fuel cell. Manifold 18 has inlet lines 22, 24 and 27
that are connected to compressed gas cylinder 16 and
first and second storage bank of hydrogen cylinders 10
and 12, respectively. Lines 22, 24 and 27 are provided
with line purge valves 26, 28 and 30 to allow inlet
lines 22, 24 and 27 to be purged upon removal of
compressed gas cylinder 16 or first and second hydrogen
storage banks 10 and 12. Additionally shutoff valves
32, 34 and 36 are provided for such purposes. For
instance, if compressed gas cylinder 16 is to be
removed, valve 32 is closed and line purge valve 26 is
open. Thereafter, compressed gas cylinder 16 is
removed from manifold 18 by simply uncoupling any one
of a number of known pressure fittings that can be
utilized for such purpose.
[0021] Manifold 18 is also provided with first,
second and third pressure regulators 38, 40 and 42
which are interposed between a junction 44 and an
outlet pressure regulator 46. First pressure regulator
38 is set at the highest pressure, for instance 90 psi
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so that hydrogen will first be drawn from compressed
gas cylinder 16. Second pressure regulator 40 which is
associated with hydrogen storage bank 10 is set at a
pressure of for instance 75 psi so that hydrogen will
next be drawn from first hydrogen storage bank 10.
Third pressure regulator 42 is set at the lowest
pressure, for instance, 60 psi so that hydrogen will
next be drawn from second hydrogen.storage bank 12.
First, second and third check valves 48, 50 and 56 are
provided to prevent flow between compressed gas
cylinder 16, first hydrogen storage bank 10 and second
hydrogen storage bank 12.
[0022] Assuming that there is no requirement for
hydrogen from the main storage site provided by first
and second hydrogen storage banks 10 and 12, the
scheduled operation of the fuel cell will cause a
solenoid valve within the fuel cell (not illustrated)
to open and the fuel cell will first draw hydrogen from
the compressed gas cylinder 16. Since pressure
regulator 38 is set at the highest pressure, second and
third check valves 50 and 56 will shut off the flow
within the legs of the manifold associated with first
hydrogen storage bank 10 and second hydrogen storage
bank 12. Outlet pressure regulator 46 will regulate
the pressure down to the supply of pressure required by
the fuel cell, for instance 50 psi. Since the amount
of hydrogen that will be consumed for purposes of
maintaining the polymer membrane in an operation
condition, periodically, compressed gas cylinder 16 can
be removed in the manner described above and renewed by
replacement with a fresh gas cylinder.
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[0023] Although not a preferred mode of operation,
manifold 18 could be designed to allow hydrogen storage
to compressed gas cylinder 16 to simply be refilled in
place by an appropriate fitting installed on inlet line
22.
[0024] Assuming that a requirement exists for the
fuel cell to power the load and that the pressure
within compressed gas cylinder 16 has not first fallen
to the pressure set in second pressure regulator 40,
hydrogen will be drawn from compressed gas cylinder 16
until pressure drops to below the pressure set point of
second pressure regulator 40. At such point, pressure
from first hydrogen storage bank 10 will cause first
check valve 48 to close and allow second check valve 50
to open. When first hydrogen storage bank 10 drops
below the pressure set for third pressure regulator 42,
second check valve 50 will close and hydrogen will be
drawn from second hydrogen storage bank 12. First and
second hydrogen banks 10 and 12 are refilled or
replaced along with compressed gas cylinder 16 after
the depletion thereof.
[0025] As may be appreciated, a mode of operation of
the present invention could be conducted without
pressure regulators 38, 40 and 42. In such case,
hydrogen could be stored at the highest pressure and
compressed gas cylinder 16 at a lower pressure in first
hydrogen storage bank 10 and yet at a lower pressure in
second hydrogen storage bank 12. This would not be
preferred due to the complexity that would be
introduced into filling operations and further if the
hydrogen were not pressure regulated, a greater amount
of hydrogen would have to be stored. Also possible is
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the use of pressure sensors and remotely activated
valves to accomplish such switch over on the depletion
of compressed gas cylinder 16 and then first and second
hydrogen storage banks 10 and 12.
[0026] With reference to Fig. 2 an alternative
hydrogen supply system 1' is illustrated. A manifold
18' is provided that has first and second inlet lines
57 and 58 that join at a junction 59. As in the
previous embodiment line purge valves 60 and 61 are
provided along with shut off valves 62 and 63. Flow
control is provided by first and second pressure
regulators 64 and 65. First pressure regulator 64 is
set at a higher pressure, for instance, at 80 psi and
second pressure regulator 65 is set at a lower
pressure, for instance, 60 psi, so that hydrogen will
initially be drawn from compressed gas cylinder 16.
Check valves 66 and 68 are provided to prevent flow
between compressed gas cylinder 16 and first and second
hydrogen storage banks 70 and 72, respectively. First
and second hydrogen storage banks 70 and 72 of
compressed gas cylinders 74 are connected to a
subsidiary manifold 76 that joins into inlet line 58 at
junction 77. Hydrogen is supplied through an outlet
line 78 after having been first reduced in pressure by
an outlet pressure regulator 79. As in the prior
embodiment, the higher pressure set point of first
pressure regulator 64 over that of second pressure
regulator 65 will cause hydrogen to be first drawn from
compressed gas cylinder 16 which can be replaced for
renewal purposes.
[0027] With reference to Fig. 3 a further hydrogen
supply system 1" is illustrated. In this embodiment,
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the auxiliary storage site is compressed gas cylinder
16 in which hydrogen stored with a pressure at about
2200 psig. The main hydrogen storage site is provided
by a composite carbon-fiber wrapped composite cylinder
80 that stores hydrogen at about 6000 psig. A manifold
18 " is provided having an inlet line 82 for hydrogen
from compressed gas cylinder 16 and an inlet line 84
for composite cylinder 80. As in previous examples,
lines 82 and 84 are provided with line purge valves 86
and 88 and shutoff valves 90 and 92. A first pressure
regulator 94 is provided to preferentially to draw
hydrogen from compressed gas cylinder 16. It can have
a higher pressure setting of about 75 psi. Second and
third pressure regulators 96 and 98 are provided for
composite cylinder 80. Since the pressure within
composite cylinder 80 is about 6000 psig, third
pressure regulator 98 is used to reduce the pressure to
2000 psi and second pressure regulator 96 is used to
further reduce the pressure below the level of that of
first pressure regulator 94, for instance 60 psi. The
hydrogen flows to a junction 100. Pressure is then
further reduced by an outlet pressure regulator 102 and
hydrogen flows from an outlet 104.
[0028] While the present invention has been
described with reference to preferred embodiments as
will occur to those skilled in the art, numerous
changes, additions and omissions may be made without
departing from the spirit and scope of the present
invention. The present invention is set forth in the
claims.
